no video in video sequence window
On the right to the preview window, you have set a proxy size to 50%. But if you don't build a proxy file, the preview can't show you a video.

So either set the Preview render to No proxy, full render, or with you video strip selected, scroll down the strip properties until you reach Proxy/Timecode and make your desired settings. Finally, to build the proxy files, have your strip selected and go to Strip -> Rebuild Proxy and Timecode indices and you're good to go.